1. Field of the Invention
The present invention relates to an interference prediction apparatus, an interference prediction method, and an interference prediction program in a computer-readable medium capable of predicting an occurrence of channel interference.
2. Description of Related Art
Recently, a wireless LAN has been rapidly distributed due to easy installation. A plurality of apparatuses is designed to wirelessly communicate with one another via the wireless LAN.
When 2.4 GHz IEEE802.11b is applied, non-interfering (non-overlapping) wireless channels include, in 2.4 GHz wireless LAN, at most three channels (for example, 1ch, 6ch, and 11ch) in the USA.
The maximum range of the wireless channel is different depending on wireless systems or countries, the number of non-interference (non-overlapped) wireless channels is also different depending on wireless systems or countries.
Accordingly, when a plurality of wireless apparatuses is used, a problem of channel interference becomes serious.
When the channel interference occurs, problems such as throughput deterioration or communication failure take place.
To avoid the channel interference caused from the aforementioned problems, it is required to use unused wireless channels that are not used by neighboring wireless apparatuses or wireless channels of which an occurrence rate of channel interference is low as communication channels.
However, much effort is needed to manually set the unused wireless channel or wireless channel of which the occurrence rate of the channel interference is low.
For this reason, Japanese Patent No. 3600568 (document 1) discloses a technique of automatically allocating an empty channel that is not used by neighboring wireless apparatuses as a communication channel.
In the technique of document 1, a beacon is detected by using an arbitrary wireless channel. When no beacon is detected, the arbitrary wireless channel used is set as a communication channel.
However, in IEEE802.11b or IEEE802.11g, the channel interference occurs in a predetermined range (for example, within a range of four wireless channels including 1ch to 4ch) of adjacent wireless channels.
Thus, even if a wireless channel in which no beacon is detected is set as a communication channel by applying the technique of document 1, channel interference may occur when a wireless channel is set as a new communication channel within a predetermined range of a neighboring wireless channel.
That is, in document 1, there is no disclosure of predicting an occurrence of the channel interference when a wireless channel is to be allocated.
Japanese Patent Application Laid-Open No. 2003-259434 (document 2) discloses a wireless communication terminal including: means for switching a communicable communication frequency by switching a frequency band used; empty state detection means for detecting an empty state of a frequency band among a plurality of frequency bands; propagation path state detection means for detecting a state of a propagation path in a frequency band among the plurality of frequency bands; and suitable frequency selection means for selecting the frequency band used on the basis of the empty state and the state of the propagation path, the wireless communication terminal selecting a frequency band that satisfies conditions from the plurality of frequency bands and enables communication.
Japanese Patent Application Laid-Open No. 2001-244901 (document 3) discloses a technique of recording a received wave together with time information as a frequency spectrum, extracting features of a spectrum pattern of the received wave by comparing the spectrum pattern of the recorded received wave with a typical spectrum pattern, and examining a use of a wave based on the features of the spectrum pattern of the received wave.
However, the technique of detecting the state of the propagation path of the frequency band in document 2, and the technique of extracting features of the spectrum pattern by comparing the spectrum pattern of the received wave with the typical spectrum pattern in document 3 are responsible for increasing costs of apparatuses.
Accordingly, it is desired to predict a wireless channel in which channel interference occurs by using existing information.
In addition, Japanese Patent Application Laid-Open No. 9-37339 (document 4) discloses a technique of retrieving a wireless communication channel that satisfies predetermined required quality conditions based on required communication types, allocating a wireless communication channel, and improving a frequency use efficiency of the wireless channel.
However, document 4 discloses improving the frequency use efficiency of the wireless channel in a mobile communication method. For this reason, even if the technique of document 4 is applied to a wireless LAN, it is impossible to avoid an occurrence of channel interference unique to the wireless LAN.
There is also a document which discloses an active or passive scan method, a spectrum, or a spectrum mask technique (see, for example, ISO/IEC 8802-11 IEEE Std 802.11 Second edition 2005-08-01 ISO/IEC 8802 11:2005(E) IEEE Std 802.11i-2003 Edition, Information technology—Telecommunications and information exchange between systems—Local and metropolitan area networks—Specific requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications (Includes IEEE Std 802.11, 1999 Edition: IEEE Std 802.11a.-1999; IEEE Std 802.11b.-1999; IEEE Std 802.11b.-1999/Cor 1-2001; and IEEE Std 802.11d.-2001)).